Make sure the seats are cleaned good,A stiff wire brush or wire cup-brush on a drill works great for cleaning chambers and seats. Carefully clamp the head in a vise,or clamp to a table. Put a few dabs of lapping compound on the valve,I do 4-dabs about 90* apart,insert valve, then rotate it with your fingers,lift,rotate drop,rotate again to spread the compound.Now attach your lapping tool,a dab of spit helps it stick to the valve. Cup your hands on either side of the tool,and oscillate it(like trying to start a fire with a stick). spin it a few times,lift valve,rotate,drop,repeat spinning,I usually do it for about 3-45-seconds total. Then Remove valve,clean seat and valve with solvent,and look at your "Margin", If you see a nice even line on the valve,about middle of the face-area of the seat,you are good,if its uneven,has spots not touched,etc..the seat needs to be cut or replaced. Looking at the seat,you should see the same continuous line,or the hits/misses. When you are done lapping,make sure to wash the head and valves with Brake-Kleen,You dont want lapping compound going thru an engine,its not a good ending. Hope this helps.
